共查询到20条相似文献,搜索用时 31 毫秒
1.
In the present study, hazelnut (Corylus avellana L.) kernel oil was transesterified with methanol using potassium hydroxide as catalyst to obtain biodiesel and a comprehensive experimental investigation of combustion (cylinder gas pressure, rate of pressure rise, ignition delay) and heat release (rate of heat release, cumulative heat release, combustion duration and center of heat release) parameters of a direct injection compression ignition engine running with biodiesel and its blends with diesel fuel was carried out. Experiment parameters included the percentage of biodiesel in the blend, engine load, injection timing, injection pressure, and compression ratio. Results showed that hazelnut kernel oil methyl ester and its blends with diesel fuel can be used in the engine without any modification and undesirable combustion and heat release characteristics were not observed. The modifications such as increasing of injection timing, compression ratio, and injection pressure provided significant improvement in combustion and heat release characteristics. 相似文献
2.
Optimal injection and ignition timings and the effects of injection and ignition timings on performance and emissions from a high-compression direct-injection stratified charge spark-ignition methanol engine have been investigated experimentally. The results have shown that direct-injection spark-ignition methanol engine, in which a non-uniform mixture with a stratified distribution can be formed, has optimal injection and ignition timings to obtain a good combustion and low exhaust emissions in the overall mode range. Both methanol injection timing and ignition timing have a significant effect on methanol engine performance, combustion, and exhaust emissions. At an engine speed of 1600 rpm, full load, and optimal injection and ignition timings, methanol engine can obtain shorter ignition delay, lesser cycle-by-cycle variation, the maximum in-cylinder pressure, the maximum heat release rate, and higher thermal efficiency compared to the case of non-optimized injection and ignition timings. For methanol engine, the optimization of injection timing and ignition timing can lead to an improvement of brake-specific fuel consumption of more than 10% compared to non-optimized case in the overall load range and engine speed of 1600 rpm. The best compromise between thermal efficiency and exhaust emissions is reached at optimal injection and ignition timings. 相似文献
3.
Arun Kumar Sikder Ralf Kleppinger Zahir Bashir G. Freudenschuss Herbert Fürst 《Polymer Engineering and Science》2020,60(11):2685-2701
Earlier, various additives werescreened to improve the weavability of poly(ethylene terephthalate) (PET) tape. For predicting the weavability, three tests had been used: tensile impact strength, fibrillar versus puckered fracture and an axial folding test. This paper shows the possibility of using a simple nano-indentation method to decide on the splintering tendency of uniaxially-oriented PET tapes, as a predictor for weavability. A plasticity index derived from the nano-indentation correlated with PET tapes that were, or were not, weavable. Nano-scratches applied parallel and perpendicular to the tape also showed differences that could be correlated to the splitting tendency. While investigating these tests methods, it was observed that pure uniaxially- oriented PET tape heat set at 140°C had a non-splintering character even without additives, while polymeric additives were needed to resist splintering for the tape heat set at 240°C. Calorimetry showed no difference in heat-of-fusion implying identical crystallinity in the tapes heat set at 140°C and 240°C. However, X-ray studies revealed that the crystallites in the tape heat set at 140°C were smaller/and or imperfect, and hence there were more lateral tie-molecules that provided it the splitting resistance. Pure PET tape if heat set below 150°C may be a workable solution for weaving, thereby dispensing with the need for toughening additives. 相似文献
4.
In this study, the effect of injection timing and EGR rate on the combustion and emissions of a Ford Lion V6 split injection strategy direct injection diesel engine has been experimentally investigated by using neat biodiesel produced from soybean oil. The results showed that, with the increasing of EGR rate, the brake specific fuel combustion (BSFC) and soot emission were slightly increased, and nitrogen oxide (NOx) emission was evidently decreased. Under higher EGR rate, the peak pressure was slightly lower, and the peak heat release rate kept almost identical at lower engine load, and was higher at higher engine load. With the main injection timing retarded, BSFC was slightly increased, NOx emission was evidently decreased, and soot emission hardly varied. The second peak pressure was evidently decreased and the heat release rate was slightly increased. 相似文献
5.
《Fuel Processing Technology》2005,86(10):1109-1126
In this paper, we explore the efficacy of (1) reducing the iodine value of soy-derived biodiesel fuels through increasing the methyl oleate (methyl ester of oleic acid) content and (2) addition of cetane improvers, as strategies to combat the biodiesel NOx effect: the increase in NOx emissions observed in most studies of biodiesel and biodiesel blends. This is accomplished by spiking a conventional soy-derived biodiesel fuel with methyl oleate or with cetane improver. The impact on bulk modulus of compressibility, fuel injection timing, cetane number, combustion, and emissions were examined. The conventional B20 blend produced a NOx increase of 3–5% relative to petroleum diesel, depending on injection timing. However, by using a B20 blend where the biodiesel portion contained 76% methyl oleate, the biodiesel NOx effect was eliminated and a NOx neutral blend was produced. The bulk modulus of petroleum diesel was measured to be 2% lower than B20, yielding a shift in fuel injection timing of 0.1–0.3 crank angle. The bulk modulus of the high methyl oleate B20 blend was measured to be 0.5% lower than B20, not enough to have a measurable impact on fuel injection timing. Increasing the methyl oleate portion of the biodiesel to 76% also had the effect of increasing the cetane number from 48.2 for conventional B20 to 50.4, but this effect is small compared to the increase to 53.5 achieved by adding 1000 ppm of 2-ethylhexyl nitrate (EHN) to B20. For the particular engine tested, NOx emissions were found to be insensitive to ignition delay, maximum cylinder temperature, and maximum rate of heat release. The dominant effect on NOx emissions was the timing of the combustion process, initiated by the start of injection, and propagated through the timing of maximum heat release rate and maximum temperature. 相似文献
6.
7.
8.
M. A. Stanish 《Drying Technology》2013,31(9):1089-1096
Drying models are created both to develop a better understanding of the governing heat and mass transfer phenomena and to assist drying practitioners in achieving commercial goals. This article is a review of the application of wood drying and kiln simulation models to commercial lumber drying challenges. Examples from the literature are briefly reviewed and four selected applications in commercial lumber manufacturing are described. They include development of equalization schedules, assessment of green lumber sorting, development of alternative drying schedules, and assessment of fan reversal frequency and timing. 相似文献
9.
10.
针对乙烯装置大型换热器现场检修中抽芯及除焦困难 ,设计了一套抽芯及除焦工装 ,经使用效果良好 ,为大型换热器的工厂化检修提供了有效途径 相似文献
11.
风冷柴油机散热片Nusselt数的数学模型研究 总被引:1,自引:0,他引:1
根据本研究元件的传热特征,编集了一组微分方程描述传热过程。同时采用模拟分析方法指导模型实验,采用综合法将实验结果表述为适合实验条件的Nusselt数经验计算公式。 相似文献
12.
Poly(L ‐lactic acid) (PLA) filaments were spun by melt‐spinning at 500 and 1850 mm?1, and further drawn and heat‐set to modify the morphology of these PLA filaments. PLA yarns were characterized by wide‐angle X‐ray diffraction (WAXD) and sonic method. WAXD reveals that PLA yarns spun at 500 mm?1 are almost amorphous while the PLA filaments spun at 1850 mm?1 have about 6% crystallinity. This is different from PET filaments spun at the same speed that have almost no crystallinity. Both drawn‐ and heat‐set PLA filaments showed much higher crystallinity (60%) than do as‐spun fibers produced at 500 and 1850 mm?1 speed, which is also higher than the usual heat‐set PET yarns. It appears that crystalline orientation rapidly reaches a value in the order of 0.95 at 1850 mm?1 and that drawn‐ and heat‐set yarns have almost the same crystalline orientation values. Molecular orientation is relatively low for as‐spun PLA yarn, and molecular orientation increased to ~0.5 after drawing or heat–setting or both. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1210–1216, 2006 相似文献
13.
14.
Experimental and analytical investigation of heat transfer to single phase flow of pseudoplastic fluids under constant heat flux condition was carried out. Experimental data for laminar flow heat transfer in the thermally developing region over a wide range of rheological properties ( n from 0.54 to 0.84 and K from 0.07 to 2.41 Nsn/m2) in 0.028 and 0.057 m diameter pipes were collected. Enhancement in heat transfer rate due to natural convection and temperature dependent rheotogy was observed. The temperature dependent viscosity effect is a function of flow behavior index and it contributes more towards heat transfer enhancement than natural convection does. A correlation (confidence level ±15%) for the entire set of data is also presented. 相似文献
15.
《Computers & Chemical Engineering》2007,31(5-6):712-721
The paper focuses on the operation of simple refrigeration cycles. With equipment given, there are, from a control and operational point of view, five steady-state degrees of freedom; the compressor power, the heat transfer in the condenser, the heat transfer in the evaporator, the choke valve opening and the active charge in the cycle. Different designs for affecting the active charge, including the location of the liquid receiver, are discussed. With a given load (e.g. given cooling duty) the compressor power is set. Furthermore, it is usually optimal to maximize the heat transfer. The two remaining degrees of freedom (choke valve and active charge) may be used to set the degree of super-heating and sub-cooling. It is found that super-heating should be minimized whereas some sub-cooling is optimal. For a simple ammonia cycle, sub-cooling gives savings in compressor power of about 2%. In this paper, refrigeration (cooling) cycles are considered, but the same principles apply to heat pumps. 相似文献
16.
17.
Low sooting combustion of narrow-angle wall-guided sprays in an HSDI diesel engine with retarded injection timings 总被引:1,自引:0,他引:1
An optically accessible single-cylinder high speed direct-injection (HSDI) diesel engine was used to investigate the spray and combustion processes with narrow-angle wall-guided sprays. Influences of injection timings and injection pressure on combustion characteristics and emissions were studied. In-cylinder pressure was measured and used for heat release analysis. High-speed spray and combustion videos were captured. NOx emissions were measured in the exhaust pipe. With significantly retarded post-top dead center (TDC) injections, smokeless combustion was achieved for wall-guided diesel spray. Premixed-combustion was observed from the heat release rates and the combustion images. Natural luminosity was found significantly lower for smokeless combustion case. However, NOx emissions were higher for the low sooting combustion cases. In addition, retarding injection timing lead to more complete combustion with more heat released from the same amount of fuel. Spray images revealed significant fuel impingement for all the conditions and the spray development was controlled and guided by the piston bowl curvature. NOx and natural luminosity trade-off trend was observed for these conditions. However, quite different from conventional diesel combustion, retarding post-TDC injection timing leads to lower natural luminosity and higher NOx emissions for narrow-angle wall-guided spray combustion. For the smokeless combustion case under moderate operating load, both homogeneous combustion and low-luminosity pool fires were observed during combustion process and the latter was due to fuel-piston impingement. The findings in this study could be used to solve the smoke issues associated with narrow-angle injection technique under high load conditions. With narrow-angle injectors, ignition could occur for significantly retarded post-TDC injections, which provides a unique mixing approach for diesel engines. 相似文献
18.
19.
为了得到水平管降膜蒸发器传热系数,建立了水平管降膜蒸发传热实验台。通过对实验结果的归纳,分析了水平管降膜蒸发器总传热系数随顶排管喷淋密度、蒸发温度的变化规律,并给出了总传热系数在水平管降膜蒸发器内部空间的分布。结果表明,总传热系数随喷淋密度、蒸发温度的增大而增大。在空间分布上,传热系数沿管长方向受凝结过程的影响前5 m先增大,后3 m逐渐减小;在垂直方向由上向下逐渐减小。另外传热系数随管排数的增加而降低,并且当喷淋密度较小时,总传热系数下降的趋势更明显。 相似文献
20.
In this paper, the air-fuel mixing and combustion in a small-bore direct injection optical diesel engine were studied for a retarded single injection strategy. The effects of injection pressure and timing were analyzed based on in-cylinder heat release analysis, liquid fuel and vapor fuel imaging by Laser induced exciplex fluorescence technique, and combustion process visualization. NOx emissions were measured in the exhaust pipe. Results show that increasing injection pressure benefits soot reduction while increases NOx emissions. Retarding injection timing leads to simultaneous reduction of soot and NOx emissions with premixed homogeneous charge compression ignition (HCCI) like combustion modes. The vapor distribution in the cylinder is relatively homogeneous, which confirms the observation of premixed combustion in the current studies. The postulated path of these combustion modes were analyzed and discussed on the equivalence ratio-temperature map. 相似文献